In Korea, although an inorganic heat insulator allowing easy handling and having flame retardancy, such as glass wools and the like, is used as a heat insulator in high temperature conditions, such as water purifiers and the like, the inorganic heat insulator has many problems in improvement of power consumption efficiency due to insufficient heat insulation properties.
Recently, a vacuum heat insulator for use at high temperatures has also been developed. As a representative example, efforts are focused on development of a vacuum heat insulator in terms of improvement in long-term performance rather than good initial performance by minimizing heat transfer in the vacuum heat insulator using a porous inorganic material such as fumed silica as a core.
However, for fundamental improvement of performance of the vacuum heat insulator, it is necessary to solve problems relating to impartment of heat resistance and flame retardancy to a shell, and increase in inner pressure of the vacuum heat insulator due to external gas and water vapor.
For high temperature electronic appliances, such as electric pots, microwave ovens and the like, although the vacuum heat insulator is prepared using, for example, a heat resistant structure of the shell and properties of a getter, there are problems such as low long-term performance, non-flame retardancy, and high manufacturing costs.
In high temperature conditions, the vacuum heat insulator can suffer from severe deterioration in long-term heat insulation properties and barrier properties of the shell.
Thus, to use the vacuum heat insulator at high temperatures, there is a need for a heat resistant shell film structure capable of minimizing deterioration in barrier properties of the shell, and a getter material capable of adsorbing large amounts of gas and water vapor flowing into the vacuum heat insulator in the high temperature conditions.
In particular, to use the vacuum heat insulator in electronic appliances, it is necessary for the vacuum heat insulator to exhibit flame retardancy and self-extinguishability.